Carbosilanes, i.e. linear or branched molecules with a backbone having alternate Si and C atoms and at least one Si—C—Si unit, are attracting attention owing to their chemical properties and potential usage in various fields such as ceramics, optical coatings, electronics, semiconductors, and hydrogen storage.
However, the synthesis of such compounds has proven to be relatively difficult, partially due to the fact that a mixture of compounds may be produced. In addition the low yield of such methods increases the cost of making the targeted compound.
Controlled Si—C—Si unit synthesis has been achieved using a Grignard method. Gevorgyan et al. (J. Org. Chem. 418, 1991 C21-C23) disclose the formation of R3Si—CH2—Si(OCH2CH2)3N from ClCH2—Si(OCH2CH2)3N and R3Si—Cl in the presence of magnesium in THF, with R3 being Me3, Me2Ph, MePh2, HMe2, or HMePh. Brondani et al. (J. Org. Chem. 451, 1993 C1-C3) disclose cross-coupling of (tri-isopropyloxysilyl)methyl Grignard reagents with organic halides to form trialkoxysilylated organic compounds. U.S. Pat. No. 5,153,295 to Whitmarsh et al. discloses that the diethylamino group of a ClSi(NEt2)2CH2Cl Grignard reagent blocks two chlorine sites preventing branching of the carbosilane polymer. U.S. Pat. No. 6,730,802 to Shen et al. discloses synthesis of 2,4,6-trimethyl-2,4,6-trisilaheptane by reducing chloromethyl-dimethylchlorosilane with lithium aluminum hydride, reacting the resulting chloromethyldimethylsilane with magnesium to form the corresponding Grignard reagent, and coupling the Grignard reagent with methyldichlorosilane.
For some specific applications, obtaining a pure product is critical for the stability of the process that uses the product, and such non-discriminating synthesis methods are costly since they involve expensive separation processes to obtain the target compound. A need remains for a cost effective synthesis method of linear or branched carbosilanes.